Enter how many time zones you're crossing and which direction to estimate your recovery time.
Most people's internal circadian clock runs slightly longer than 24 hours, which makes it naturally easier to delay sleep (as westward travel requires) than to advance it (as eastward travel requires). This is why eastward jet lag typically takes noticeably longer to shake than westward jet lag over the same number of zones.
Basis: circadian rhythm research on jet lag recovery; the default rates above (~1 day per zone eastward, ~0.5 day per zone westward) are the commonly cited rule of thumb; sources differ, and some studies report closer to 1 day per zone in either direction. Individual recovery varies with age, sleep habits, and light exposure — adjust the rates above if you know your own pattern differs. Not medical advice.